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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 875 · 40 questions
TalentJR

Developer's tip (Compare with the comment): Read each line and its comment (after //): does the code do exactly that? Actual = run the lines as written. Expected = follow every comment. After the fix, test again.

NameDateTime takenScore ___ / 40
  1. 1.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 37; // start at 37
    line 2: coins = coins + 2; // double it
    line 3: coins = coins + 5; // add 5
    line 4: show(coins); // show it
  2. 2.🐞 After fixing a bug you should ___. (a) never test (b) test it again (c) delete the test (d) release at once
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 36; // start at 36
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // double it
    line 4: stars = stars + 4; // add 4
    line 5: show(stars); // show it
  4. 4.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 34; // start at 34
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars - 2; // take away 2
    line 4: stars = stars - 6; // add 6
    line 5: show(stars); // show it
  5. 5.🐞 Finding and fixing bugs is called ___. (a) decorating (b) downloading (c) designing (d) debugging
  6. 6.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 41; // start at 40
    line 2: points = points * 2; // double it
    line 3: points = points + 6; // add 6
    line 4: show(points); // show it
  7. 7.🐞 A comment in code (after //) is for ___. (a) the app store (b) the battery (c) people reading the code (d) the phone screen
  8. 8.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 53; // start at 50
    line 2: lives = lives - 5; // take away 5
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 39; // start at 39
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins + 1; // take away 1
    line 4: show(coins); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 32
    line 2: score = score - 4; // take away 4
    line 3: score = score - 4; // take away 4
    line 4: show(score); // show it
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 45; // start at 42
    line 2: points = points * 2; // double it
    line 3: points = points - 5; // take away 5
    line 4: points = points + 5; // add 5
    line 5: show(points); // show it     (a) line 1 (b) line 3 (c) line 2 (d) line 4
  12. 12.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 49; // start at 49
    line 2: lives = lives + 8; // add 5
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it
  13. 13.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 49; // start at 48
    line 2: score = score * 2; // double it
    line 3: score = score - 1; // take away 1
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  14. 14.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 32; // start at 32
    line 2: points = points - 3; // add 3
    line 3: points = points * 2; // double it
    line 4: points = points + 5; // add 5
    line 5: show(points); // show it
  15. 15.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives - 2; // take away 2
    line 4: lives = lives - 3; // add 3
    line 5: show(lives); // show it     (a) line 3 (b) line 1 (c) line 2 (d) line 4
  16. 16.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 43; // start at 42
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it     (a) line 3 (b) line 1 (c) line 2 (d) line 4
  17. 17.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 49; // start at 49
    line 2: coins = coins + 2; // double it
    line 3: coins = coins + 3; // add 3
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it
  18. 18.🐞 What is a good first step when an app gives a wrong result? (a) find where it goes wrong (b) add more colours (c) delete the app (d) buy a new phone
  19. 19.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 50; // start at 50
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // add 2
    line 4: stars = stars + 5; // take away 5
    line 5: show(stars); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  20. 20.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 47; // start at 47
    line 2: points = points - 2; // take away 1
    line 3: points = points + 5; // add 5
    line 4: show(points); // show it
  21. 21.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 51; // start at 50
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives - 3; // take away 3
    line 4: show(lives); // show it
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 40; // start at 40
    line 2: score = score + 5; // add 5
    line 3: score = score + 5; // take away 5
    line 4: score = score - 3; // take away 3
    line 5: show(score); // show it
  23. 23.🐞 What is a bug? (a) a fast phone (b) a mistake in the code (c) a new feature (d) a nice icon
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 45; // start at 45
    line 2: score = score * 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score * 3; // double it
    line 5: show(score); // show it
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 47; // start at 45
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 2; // take away 2
    line 4: lives = lives - 8; // take away 5
    line 5: show(lives); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 39; // start at 39
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives + 2; // double it
    line 4: show(lives); // show it     (a) line 2 (b) line 3 (c) line 1
  28. 28.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 48; // start at 46
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars + 4; // add 4
    line 4: stars = stars + 6; // add 6
    line 5: show(stars); // show it
  29. 29.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 41; // start at 41
    line 2: score = score + 5; // add 5
    line 3: score = score - 4; // take away 4
    line 4: score = score + 5; // add 2
    line 5: show(score); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 40; // start at 40
    line 2: points = points * 3; // double it
    line 3: points = points + 6; // add 6
    line 4: show(points); // show it
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 4; // add 4
    line 4: stars = stars + 2; // double it
    line 5: show(stars); // show it
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 35; // start at 35
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives - 7; // take away 4
    line 5: show(lives); // show it
  33. 33.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 30; // start at 30
    line 2: stars = stars + 2; // double it
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 43; // start at 42
    line 2: score = score * 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score + 2; // add 2
    line 5: show(score); // show it     (a) line 2 (b) line 3 (c) line 4 (d) line 1
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 39; // start at 39
    line 2: score = score + 2; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 52; // start at 49
    line 2: stars = stars - 1; // take away 1
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  37. 37.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 49; // start at 49
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 2; // add 2
    line 4: lives = lives + 2; // take away 2
    line 5: show(lives); // show it     (a) line 4 (b) line 1 (c) line 3 (d) line 2
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 35; // start at 35
    line 2: score = score * 3; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 42; // start at 42
    line 2: points = points - 3; // take away 3
    line 3: points = points + 2; // double it
    line 4: show(points); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 36; // start at 36
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives - 2; // add 2
    line 4: lives = lives + 5; // add 5
    line 5: show(lives); // show it

Answer key

  1. 44
  2. test it again
  3. 78
  4. 41
  5. debugging
  6. 86
  7. people reading the code
  8. 41
  9. 45
  10. 25
  11. line 1
  12. 216
  13. line 1
  14. 75
  15. line 4
  16. line 1
  17. 104
  18. find where it goes wrong
  19. line 4
  20. 51
  21. 45
  22. 37
  23. a mistake in the code
  24. 540
  25. 82
  26. line 4
  27. line 3
  28. 54
  29. 44
  30. 126
  31. 76
  32. 133
  33. 59
  34. line 1
  35. 156
  36. 204
  37. line 4
  38. line 2
  39. 41
  40. 41

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